DOCSIS is a protocol that is used to send digital video and data from a hub or headend facility (HEF) to a cable modem (CM) at a customer premise. Digital video is a one-way or downstream application from the hub to the CM, e.g., a television program, while data services are two-way (downstream and upstream) applications, e.g., Internet Protocol (IP) web browsing or IP telephony. For downstream transport, both digital video and data are encapsulated using the DOCSIS and Motion Picture Experts Group (MPEG) protocols prior to transport. To preserve the integrity of video and data during transport error correction techniques are employed, e.g., forward error correction (FEC) and interleaving as defined in the International Telecommunication Union (ITU)-T J.83 standard.
DOCSIS version 3.0 expands DOCSIS capability beyond a single downstream RF carrier to multiple downstream RF carriers using a technique known as bonding or channel bonding. Channel bonding essentially uses packet multiplexing across two or more downstream RF carriers and is visible at layers 2-4 of the Open System Interconnection (OSI) Reference Model, e.g., TCP/UDP-IP-Ethernet/DOCSIS layers. When using a large number of carriers, e.g., 32, 64 or greater, DOCSIS 3.0 channel bonding becomes complex due to the DOCSIS signaling requirements and a quality of service (QoS) queue is required for each transmit queue on a per-carrier basis. In addition, the RF carriers and packets under DOCSIS 3.0 bonding are unsynchronized and require reassembly of the data stream at the CM.